We propose to develop a series of products to perform percutaneous cryosurgery on cancers of the prostate, liver, brain and pancreas. Because of the morbidity, mortality and high costs associated with currently available treatment modalities for prostatic cancers, percutaneous cryosurgery under transrectal ultrasound guidance could potentially provide much less morbid treatment and should prove to be a more desirable mode of treatment. The specific aims of this study is the following: I. to determine the ideal performance characteristics for ultrasound probes and the other equipment needed to perform a safe, simple cryosurgical procedure II. to develop medical suitable instruments (cryoprobes) with which to perform cryosurgery using newly developed technology. III. to assess the safety and efficacy of percutaneous prostate cryosurgery under ultrasound guidance using the developed instruments.